https://bugs.kde.org/show_bug.cgi?id=397778
Bug ID: 397778
Summary: SMB access causes ecryptfs counter
/dev/shm/ecryptfs-$USER-Private to decrement but not
increment causing KDE apps to lose access to home
directory
Product: kwallet-pam
Version: 5.12.6
Platform: Neon Packages
OS: Linux
Status: UNCONFIRMED
Severity: normal
Priority: NOR
Component: general
Assignee: plasma-b...@kde.org
Reporter: nick.craig....@gmail.com
Target Milestone: ---
I've no idea what KDE product or component this goes under or whether the
problem is caused by a KDE component, however because the end result of the
problem is the ecryptfs directory being umounted causing lots of KDE app write
errors I thought it best to report it here.
To reproduce this bug you need Samba installed with the smbd deamon running and
you need to have your home directory encrypted using ecryptfs. You also need to
create a shared directory, that is publically available ie requires no login.
Example.
You have a Windows 10 system on your network, you access the shared directory
and after a while you get write errors from any apps (KDE or otherwise) you are
using. This is because the ecryptfs directory has unmounted.
Whether the ecryptfs unmounts is determined by the counter
/dev/shm/ecryptfs-$USER-Private. Typically after KDE starting this counter is
either 1 or 2 and with each new user login e.g. ALT-F1/F2 etc the counter
increments and then decrements when the user logs out. Eventually when
everybody logs out, including the KDE desktop user the counter goes to 0 and
the ecryptfs un-mounts.
The problem is when an smb access occurs the counter never increments however a
few seconds later it always decrements. This causes the counter to reach 0
prematurely and the home directory is unmounted. Problem is your KDE desktop is
still running and now KDE and any apps your running at the time can't access
the home directory and KDE reports unable to write this config file etc..
So is this an smb issue, an ecryptfs issue or does KDE update the
/dev/shm/ecryptfs-$USER-Private counter ? making it a KDE issue.
I know ecryptfs has an auto mount/umount feature which is implemented in my
setup e.g. the files /home/$USER/.ecryptfs/auto-mount (zero length file) and
/home/$USER/.ecryptfs/auto-mount (zero length file) both exist.
Is it because I'm sharing a folder via smb that doesn't require authentication
and that's causing the discrepancy between the increment and decrement of the
/dev/shm/ecryptfs-$USER-Private counter ?
I know there are other options for accessing smb shares such as sftp etc but
this problem also occurs by simply having a windows system on the same network,
on the windows system you don't even need to access the share as I guess
windows automatically looks around to see what else is on the network in the
background. This causes a linux system to lose access to its encrypted home
directory.
This is a long standing issue going back years, 100% reproducible and has been
seen on multiple versions of Kubuntu and also on KDE Neon which I'm now
running.
Any help appreciated.
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